This invention relates to the field of electrophotographic image printing systems. More particularly, the present invention relates to apparatus and methods for preventing damage to printing cartridge and printer components prior to first use.
Laser printers have become the printers of choice for most businesses and many individuals. Laser printers typically produce text and graphics of excellent quality at relatively high speeds.
Modern laser printing is generally accomplished by what is commonly known as the electrophotographic process. At the heart of the imaging process is an organic photoconductive (OPC) drum. The drum typically includes an extruded aluminum cylinder coated with a non-toxic organic photoconductive material. There are six generalized stages to the electrophotography process: cleaning, conditioning, writing, developing, transferring and fixing.
Cleaning is the first stage in the imaging process. This stage prepares the OPC drum to receive a new latent image by applying a physical and electrical cleaning process. The physical cleaning of the OPC is typically accomplished by a drum cleaning blade (or wiper blade) and a recovery blade. The wiper blade scrapes any excess toner from the drum and the recovery blade catches the toner and sweeps it into a waste hopper. In the electrical aspect of cleaning, the previous image on the drum must be cleared before a new one may be applied. The electrical cleaning of the OPC drum is performed by erasure lamps (usually corona wire technology) or a primary charge roller (PCR), which eliminate the previous latent image from the drum.
After the drum has been cleaned, it must be conditioned or charged to accept the image from the laser. A primary corotron (corona wire or PCR) applies a uniform negative charge (usually in the range of xe2x88x92600V to xe2x88x92720 V DC) to the surface of the drum.
Following the conditioning stage is the writing stage. In this stage, a laser beam is used to discharge a conditioned charge to the drum surface. The conditioned charge creates a latent image on the drum. An aluminum base is connected to an electrical ground and the photoconductive material comprising the OPC becomes electrically conductive to ground when exposed to light (generally a laser). Therefore, the negative charges deposited onto the surface of the drum conduct to the aluminum base when exposed to light, creating the latent image. The latent image area will attract toner in a later stage.
The fourth stage is developing. At this stage, the latent image becomes a visible image. This stage generally requires four major components: toner, a developer roller assembly, a metering blade, and an AC/DC charge. Toner is attracted to the developer roller either by an internal magnet or by an electro-static charge. The roller carries the toner particles to a metering blade (a/k/a a doctor blade), where toner tumbles and creates a tribo-electric charge (friction) on the surface of the toner particles. The metering blade then provides for an evenly distributed amount of toner to pass to the OPC drum. Once the toner particle has passed beyond the doctor blade, it is ready to be presented to the OPC drum. The developer roller is then charged with an AC/DC charge from the High Voltage Power Supply. This charge allows the toner particles to xe2x80x9cjumpxe2x80x9d from the developer roller and travel to the OPC drum where it is attracted to the latent image.
At this point, the toner image on the drum is transferred onto a sheet of paper. As the paper is passed under the OPC drum, it is passing over a transfer corotron assembly. The transfer corotron assembly includes a transfer roller and places a positive charge on the back of the page, attracting the toner from the drum.
The sixth and final stage is fixing. Also known as fusing, this is the stage in which the toner is permanently affixed to the paper. The fuser assembly typically includes a heated roller, a pressure roller, a heating element, a thermistor, a thermal fuse, and, sometimes, a cleaning pad. The heating element is typically placed inside the heated roller, which is usually constructed of aluminum with a teflon coating. The roller is heated to approximately 350xc2x0 F. (180xc2x0 C.). The second roller is usually a rigid foamed silicon rubber. This second roller applies pressure to the heated roller. The paper passes between the two rollers and the heated roller melts the toner particles while the pressure roller presses the toner into the fiber weave of the paper.
In many laser printers, the OPC drum, PCR, developer roller, and toner particles are part of a disposable cartridge that can be replaced from time to time as the supply of toner is exhausted. Most often, when a laser printer is transferred from one place to another, the laser printer does not include an installed cartridge. The primary reason cartridges are not installed during transport is to prevent damage to cartridge components, printer components, or both. When a cartridge is properly installed in a laser printer, there are sensitive interfaces between the PCR and the OPC; and between the OPC and the transfer roller. In some printers, there may also be a sensitive interface between the developer roller and the OPC. Even with carefully packaged printers, rough handling of a laser printer with an installed cartridge can damage the PCR, OPC, and/or the transfer roller. The interface spacing and tolerances may also be compromised during shipping and handling, which may reduce image quality. Therefore, it is uncommon at present to ship laser printers with cartridges installed.
Further, for color laser printers there may be additional sensitive interfaces that may be damaged during shipping and handling with a toner cartridge installed. The additional surfaces may include interfaces between an intermediate transfer drum or belt and the OPC, and the intermediate transfer drum or belt and a secondary transfer roller.
However, because many users prefer to have a cartridge immediately available when a laser printer is purchased, the packaging of new laser printers often includes a separate cartridge not installed in the printer. For example, it is common to ship new laser printers in a configuration shown in FIG. 1, with a printer (22), a cartridge (20), and one or more printer accessories (14) housed in a box (16) but separate from one another. The packaging for printer (22), cartridge (20), and printer accessories (14) also commonly includes some sort of outer material such as polystyrene or bubble wrap to reduce handling shock.
The arrangement shown in FIG. 1, however, requires a much larger box (16) than the dimensions of printer (22) and accessories (14) alone would require. In addition to the higher environmental and economic costs associated with larger boxes, shipping expenses are increased because of the large box size. Because most bulk shipping rates are priced on volumexe2x80x94rather than massxe2x80x94shipping costs for laser printers could be significantly reduced by installing the cartridge in the printer before shipment and housing the printer and cartridge in a smaller box. However, the risk of damage to printer and cartridge components has presently outweighed the potential benefit to lower shipping and packaging costs in most instances.
The present invention provides, among other things, an electrophotographic printer including a transfer roller having a first movable spacer for temporarily creating a gap between the transfer roller and a photo conductor.
The present invention also provides a method of packaging an electrophotographic printer for shipment including inserting a toner cartridge into the electrophotographic printer with a first self-removing spacer between a transfer roller and a photoconductive drum prior to shipment.